Submission #724391

#	Time	Username	Problem	Language	Result	Execution time	Memory
724391		chanhchuong123	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	773 ms	138752 KiB

tracks

#include <bits/stdc++.h>
using namespace std;
#define task ""
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (b), _a = (a); i >= _a; --i)

template <typename T1, typename T2> bool minimize(T1 &a, T2 b) {
	if (a > b) {a = b; return true;} return false;
}
template <typename T1, typename T2> bool maximize(T1 &a, T2 b) {
	if (a < b) {a = b; return true;} return false;
}

const int dx[] = {-1, 0, 0, +1};
const int dy[] = {0, -1, +1, 0};

const int MAX = 4000;
int n, m;
int ans = 0;
int d[MAX][MAX];
char a[MAX][MAX];

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	if (fopen(task".inp", "r")) {
		freopen(task".inp", "r", stdin);
		freopen(task".out", "w", stdout);
	}

	cin >> n >> m;
	for (int i = 0; i < n; ++i)
        for (int j = 0; j < m; ++j)
            cin >> a[i][j];
    memset(d, 0x3f, sizeof d);
    deque<pair<int, int>> dq;
    dq.push_front({0, 0});
    d[0][0] = 1;
    while (dq.size()) {
        int u = dq.front().fi;
        int v = dq.front().se;
        maximize(ans, d[u][v]);
        dq.pop_front();

        for (int i = 0; i < 4; ++i) {
            int x = u + dx[i], y = v + dy[i];
            if (x < 0 || x >= n) continue;
            if (y < 0 || y >= m) continue;
            if (a[x][y] != '.') {
                int w = a[u][v] != a[x][y];
                if (minimize(d[x][y], d[u][v] + w)) {
                    if (w) dq.push_back({x, y});
                    else dq.push_front({x, y});
                }
            }
        }
    }
    cout << ans;
	return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'int main()':
tracks.cpp:32:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   32 |   freopen(task".inp", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:33:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   33 |   freopen(task".out", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 30 / 30
• Subtask 2: 70 / 70